The Sima I-mix 100 is a "digital jukebox" and stores up to 8.4Gb of mp3 music on its internal hard drive, good for around 8000 minutes of music playing time. I really like being able to choose any song at the touch of a button from my collection. Very handy because I was able to download a bunch of my brother's CD's and pick only the songs I wanted. The sound quality is very good (128kbps mp3 format), very difficult to tell apart from a CD. These are available commercially for around $400 and the larger model, the I-mix 120 (20Gb hard drive) for ~$550.
I have only two complaints: 1) While the random play mode is a pseudo-random number generator, there is no way to "seed" it with a random event (like the time on a clock), so you get the same "random" sequence every time to turn it on, unless you have added songs. Luckily (?)if you hit the back (<--) button while in random paly mode, you don't get the last song you heard, but a totally different new random one, so if you turn it on with the random play mode, you only have to hit back and forward buttons a few times to get an entirely different "random" sequence. 2) The I-mix can only do one thing at a time. If you are buzzing around through the menus while playing a song, you hear blips in the music (not too noticeable). You also cannot delete songs or even remove a CD while playing from another source (like the hard drive). Both of these complaints are only a minor inconvenience and would probably double the cost of the item to correct.
To get a song onto the hard drive, you simply pick the songs you want (or the whole cd) and hit record. You can also download mp3's from your computer directly through the parallel port. It takes about 10 minutes to download a whole 60 minute CD. To change the names from "artist0000" "track001" and "album0000" to useful names, you can enter them through the remote (difficult and slow) or use the provided software to type them through the parallel port (easier). The software is pretty simple, but had poor instructions and explanations and took me (pretty computer literate) about 10 minutes to install and 15 minutes to figure out how to use. Once you get the hang of it, it is the way to go. For playlists, you must use the remote, which is a little time consuming, unless you just highlight artists instead of individual songs. Once you save a playlist, you cannot directly append to it, so here's what I do: 1) mark the playlist you want to append to; 2) mark the other songs to want to add; 3) hit "prog", then "save" and change the name to what the old list was; 4) delete the old list (since two lists of the same name are allowed and not overwritten).
I really love this item and have recommended it to several friends. Check ebay, I got mine new in the box for less than $300. The Sima webpage is "http://www.simacorp.com/imix100.html". It gets to songs much faster than those 100 CD changers, and it's more convenient, because you can download and upload songs.